BALANCING RADIATION AND CONTRAST MEDIA DOSE IN SINGLE-PASS CONTRAST-ENHANCED MULTI-DETECTOR CT: PROSPECTIVE EVALUATION OF IMAGE QUALITY

RATIONALE and OBJECTIVE: As both contrast and radiation dose affect the quality of CT images, a constant image quality in abdominal contrast-enhanced multi-detector CT (CE-MDCT) could be obtained balancing radiation and contrast media dose according to the age of the patients. MATERIALS AND METHODS: Seventy-two (38M;34F; aged 20-83 years) patients underwent a single-pass abdominal CE-MDCT. Patients were divided into three different age-groups: A(20-44 years); B (45-65 years); C (> 65 years). For each group, a different Noise Index (NI) and contrast media dose (370 mgI/mL) was selected as follows: A (NI=15; 2.5 mL/kg); B (NI =12.5; 2 mL/kg); C (NI=10; 1.5 mL/kg). Radiation exposure was reported as Dose Length Product (DLP) in mGy*cm. For quantitative analysis, Signal-to-Noise (SNR) and Contrast-to-Noise (CNR) ratios were calculated for both the liver (L) and the abdominal aorta (A). Statistical analysis was performed with a one-way ANOVA. Standard imaging criteria were used for qualitative analysis. RESULTS: Whereas peak hepatic enhancement was 152±16, 128±12 and 101±14 HU (p <0 .001) for Group A, B and C, respectively, no significant differences were observed in the corresponding SNRL with 9.2±1.4, 9.1±1.2 and 9.2±3. Radiation (mGy*cm) and contrast media dose (mL) administered were 476±147 and 155±27 for Group A, 926±291 and 130±16 for Group B and 1981± 451 and 106±15 for Group C, respectively (p < 0.001). None of the studies was graded as poor or inadequate by both readers and the PABAK ranged between 0.48 and 0.93 for all but one criteria. CONCLUSIONS: A constant image quality in CE-MDCT can be obtained balancing radiation and contrast media dose administered to patients of different age.